Steam-engine indicator.



Patented Dec. 24, |90l.

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(Application Bled De. 10, 189B.)v

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UNITED STATES PATENT O'EEICE.

JOHN CLARK DOBBIE, OF GLASGOW, SCOTLAND.

STEAM-ENGINE IINDICATOR.

' SPECIFICATION forming part-of Letters Patent No. 689,640, dated December 24, 1901.

Application filed December 10, 1898.. SeralNo. 698,851. 4(No model.)

To all whom it' may oon/cern.-

Be it known that I, JOHN CLARKDOBBIE, a citizen of the United Kingdom of Great Britain and Ireland, and a resident ot' 45 Clyde 5 Place, in the city of Glasgow, Scotland, have'd 1o of which the following is a specification.

This invention has for its object to simplify and improve the construction of steam-en gine indicators.

The invention is illustrated by the accompanying drawings.

Figure l is a vertical section, and Fig. 2 a plan, of a steamengine indicator as constructed under my invention. Fig. 3 is a section and elevation, on a large scale, of a jaw in which is pivoted the lower end of the link C; and Fig. 4 is an elevation of the same on a plane at right angles to that of Fig. 3. Fig. 5 is a plan of the arm which carries the pencil. Fig. 6 is a plan of the radius-link in which said arm is pivoted. Fig. 6a is an elevation of the link C,which connects said radius-link with the piston-rod of the indicator. Fig. 7 is a vertical section of the drum-spring and related parts. Fig. 8 is an elevation on a plane at right angles to that of- Fig. 7, and Fig. 9 is a plan of the saine.

Referring to Figs. l and 2A, in order to obviate overhanging of the arm A, carrying the indicator pencil A', to clear the upright bracket B, on which the radius-link O, connecting the arm A to the link C', is centered, the said arm A is according to the present invention formed with a downwardly-projecting knee or branch A2, to the lower end of which the radius-link C is jointed, and the outer end of the indicator-arm is curved or bent downward over the upright bracket B, so that its extremity carrying the pencil may reach to the bottom of the card-drum E when the piston-rod F of the piston F' is at its lowest point and traverse the length of the drum E in a Vertical line as the piston-rod F rises. The

radius-link C is connected to a link C', which is in turn connected to a jaw F,4 on the upper end of the piston-rod F, said jaw F4 being constructed as shown to enlarged scale at Figs. 3 and 4 and screwed into the tubular piston-rod F.

f The helical spring G, which is provided to counterbalance the steam-pressure and is usually placed within the upper end of the cylinder H, containing the moving piston F' of the indicator, is rendered' more readily accessible for removal and interchanging by cutting a chamber I2 through and through the upper part of the upwardV extension I', the walls of the chamber forming nprights which carry the framing I or are formed integral therewith, thesaid spring Gbeing accessible through said chamber l2. The piston-rod F, where it is inclosed by the spring G, is divided and one length is screwed into the other or joined thereto by a screwed piece F2, while a vulcanite or other non-conducting ferrule or collar F3, on which the spring G bears, is secured on the piston-rod F to provide for unscrewing one part of the rod Ffrom the other. By separating the meeting ends of the divided piston-rod F the spring G can be withdrawn and replaced.

The barrel or drum E, on which lthe indicating-paper J is wound, is set on a pulley which is pivoted on the framing I. The cylindrical flange I3 of said pulley is cut out to form prongs, as shown, which clamp on the said drum E. The indicator-card J is securedto the drum E and the latter held down on its seat on the pulley by a blade-spring K, attached at its lower end to the pulley, eX- tending up the side oflthe drum E and terminated at its upper end in a catch K', which engages with a notch E in the upper end of the drum E. The drum-spring M is fitted with a head M', having an internal screw thread the convolutions of which are lefthanded when those of the spring M are right handed and which is screwed onto a screwthreaded stem M2 in the center of the cordbed I. A device for screwing the head M of the drum-spring M onto its spindle M? is shown at Figs. 7, 8, and 9 and consists of a bridge-piece L, having notches L' at its lower end,which engage projections M3 on the drumhead M', the actuating-handles L2 of this bridge-piece being carried through to engage and raise the head M"1 at the upper edge of the spring M from the square portion M5 of the spindle M2.

The pencil-arm A and also the radins-link are constructed, as shown at Figs. 5 and G, with bosses around their connecting-eyes.

Having now described the invention, what I claim, and desire to secure by Letters Patent, is-

The combination in a steam-engine indicatorof a cylinder adapted to be connected with the cylinder of the steam-engine, a piston F therein adapted to be moved in one direction by the steam-pressure, a jointed piston-rod F connected with said piston F', a coiled spring G adapted to move said piston Il" in a direction opposite to the steam-pressure, a link C pivotally connected with said pistonrod F, a radius-link C pivoted on the outer end of said link C at the middle part of said link C, a curved oscillating bracket B pivoted at its lower end to a stationary support and at its upper end to one end of said radiuslink C, a pencil-carrying arm A pivoted at its outer end to an upright oscillating arm, a knee AL on said arm A pivotally connected with the end of said radius-link C opposite to said bracket B, and a rotating paper-carrying drum E adjacent to the free end of said pencil-carrying arm A whereby a pencil on said arm A marks a diagram on the paper on said drum E, substantially as described.

In witness whereof I have hereunto sot my hand in presence of two Witnesses.

JOHN CLARK DOBBIE.

Witnesses: V

WALLACE' FAIRWEATHER, J No. ARMSTRONG, Jnnr. 

